Lappys… OK, you dont need one with some DJ playout systems, like the MCX8000 in Standalone mode, or with the SC5000 Primes… but generally, MIDI programs, like Serato, Virtual DJ and Traktor, all need a lappy running for the entire length of the show/slot.

Latency is of course something to be avoided. For newer members of the forum, and/or those new to DJing with a lappy… Latency is the lag between a button or other control being pushed or pressed or rotated, and the DJ software actually responding to that user action. If latency is low, such as 5milliseconds then the delay, lag, or latency isnt noticable. Of course, if the latency is more like 200milliseconds (a fifth of a second) then it’s a bit more noticable. You might well be pressing things, absolutely dead on the beat, but the lappy is responding a fraction of a second later. That sort of lag isnt noticable or important for those using a lappy for Word Processing or a nice spreadsheet, but for DJing…where split second timing is paramount… it’s very noticable.

In my experience, latency has to do with the sound output, not with the controls (and is tightly linked to the audio-buffer size).

While clearly there can be latency between an external (midi) command and the response from the software and some of the reasons that cause one can contribute to the other, changing buffer size for audio is usually the quick fix for that problem, while getting rid of system latency for the issue you describe takes more system tuning outside of the DJ system.

Perhaps we should have two different words for both or at least add something like “audio” and “control” in front of “latency” to avoid confusion?

Sorry for covering this in a detailed way, when I suspect you’re already clear on it. But some members might not be as equally up on it as others.

If there was no latency or 0 milliseconds latency then every button you press, every platter move that you make etc would be heard to be happening and reacting to you instantly.

However, the more things that a computer has to think about, the less the more chance of something not happeneing on-time or in-time, there is. This would include new music data reaching the sound card in time - when music data doesn’t reach the sound car in time, then distortion, gaps, crackles and staggered audio is heard. An audio buffer of a few milliseconds helps to resolve issues.

Occasionally, a question pops up on forums along the lines of “I have an xyz123 midi controller. What latency should I set?” Unfortunately it’s not the same answer for every owner as the latency is all down to how fast can the users lappy think about all the things that that particular lappy has to think about.

So latency will different for everyone’s overall setup and latency. The more optimised the lappy, the faster it is able to process, the less background processes are running etc, the more the lappy is able to think about the task in hand. You DJing.

When the processor gets hot it throttled back (slows down) to help it cool down a bit. This means the lappy is less able to think about all those things going on, as well as it could when it was cold. This could mean that at the beginning of an evening you could has audio latency set to 5ms-10ms (on a pretty fast lappy) but the same lappy in the same set up might need a latency of 20ms-50ms latency setting once the processor is Hot a couple of hours later as the processor may be throttling back (taking its foot off of the gas). The extra few milliseconds buffer gives the sound card a little extra breathing time for the lappy to send music data to the sound card, avoiding those crackles, stutters and distortion.